Separation of nickel from asbestos ore

ABSTRACT

The nickel-alloy awaruite found in chrysolite asbestos ore tailings is concentrated by magnetically separating the asbestos ore tailings to obtain a magnetically attracted, nickel-enriched fraction. The nickel-enriched fraction is mechanically impacted, preferably by ball milling, to increase the maximum dimension of the awaruite particles and to fracture the other more easily ground material in the tailings, mainly magnetite and serpentine rock, into smaller particles. After the maximum dimension of the awaruite particles has been increased, they can be efficiently size-separated from the smaller particles of fractured magnetite and serpentine.

United States Patent Fowler 5] Feb. 29, 1972 [54] SEPARATION OF NICKELFROM ASBESTOS ORE Richard Payson Fowler, Somerville, NJ.

[72] Inventor:

[73] Assignee: Johns-Manville Corporation, New York,

[22] Filed: Aug. 31, 1970 [21] Appl. No.: 68,443

[52] US. Cl. ..24l/4, 241/24, 209/39 [51] Int. Cl. ..B03c 1/30 [58]Field of Search ..241/20, 24, 25, 27, 30, 79, 241/81; 209/4, 39

[56] References Cited UNITED STATES PATENTS 2,500,154 3/1950 Crocket..241/4 X 2,723,029 11/1955 Lawver ..241/79X 3,022,956 2/1962 Haseman..24l/24 3,372,803 3/1968 De Lisleetal ..24l/4X PrimaryExaminerGranville Y. Custer, Jr. Attorney-John A. McKinney and Robert M.Krone [57 1 ABSTRACT The nickel-alloy awaruite found in chrysoliteasbestos ore tailings is concentrated by magnetically separating theasbestos ore tailings to obtain a magnetically attracted, nickelenrichedfraction. The nickel-enriched fraction is mechanically impacted,preferably by ball milling, to increase the maximum dimension of theawaruite particles and to fracture the other more easily ground materialin the tailings, mainly magnetite and serpentine rock, into smallerparticles. After the maximum dimension of the awaruite particles hasbeen increased, they can be efficiently size-separated from the smallerparticles of fractured magnetite and serpentine.

10 Claims, 1 Drawing Figure Patented Feb. 29, 1972 3,645,454

uwau'roa RICHARD F. FOWLER ATTORN EY SEPARATION OF NICKEL FROM] ASBESTOSORE BACKGROUND OF THE INVENTION This invention relates to a physicalprocess for obtaining a concentrated nickel-containing product fromchrysotile asbestos ore. More particularly, the invention relates to aphysical process for concentrating the awaruite particles (FeNi that arefound in asbestos ore in low weight percentages.

Nickel is present in small amounts in some asbestos ores in the form ofawaruite, a metallic alloy with iron (FeNi For example, theconcentration of nickel in tailings from asbestos ore milling operationsmay be about 0.2 percent by weight. In general, granular fractionsobtained from asbestos-milling operations tend to contain more nickelthan fibrous materials and sifter undersizes. It should be noted,however, that the nickel content of asbestos ore found within specificlocations within the same mine can vary widely.

Nearly the entire nickel content of chrysotile asbestos ore is in theform of particles of awaruite which are intimately associated with othermaterials including the fibrous chrysotile asbestos and serpentine rock.Small quantities of magnetite are also usually found in the ore.

The awaruite is magnetic and can, like the magnetite, be magneticallyconcentrated from the screen undersize material resulting from millingasbestos ore. However, much serpentine rock remains with themagnetically separated material, which precludes successful smeltingoperations and economical chemical recovery methods.

In the past, efforts were made to develop processes to recover thenickel from asbestos tailings, but the residual asbestos fiber and thelarge amount of serpentine rock associated with the awaruite in thetailings has prevented the inexpensive concentration of the nickel. Noprocess has previously been developed that has proved commerciallyfeasible.

OBJECTS OF THE INVENTION A principal object of the present invention isto provide a commercially practicable process for recovering nickel fromasbestos ore tailings, that is a process which produces nickel having avalue greater than the cost incurred in practicing the process.

It is another object of the invention to provide a process that producesa highly concentrated nickel'containing product that can be readily usedin steelmaking processes.

Still another object of the invention is to provide an economicalmechanical process for concentrating the awaruite present in asbestosore.

Additional objects and advantages of the invention will be set forth inpart in the description which follows or will be obvious from thedescription, or may be learned by the practice of the invention.

SUMMARY OF THE INVENTION The invention provides a process forconcentrating the nickel alloy awaruite found in asbestos ore tailings.Asbestos ore tailings, preferably granular mill fractions having a majorportion of the asbestos fiber removed, are magnetically separated toobtain a magnetically attracted, nickel-enriched fraction and a wastefraction. The nickel-enriched fraction is The process of the inventionpermits efficient recovery of nickel from asbestos ore tailings. It hasbeen known for years that certain asbestos ore tailings contain nickelbut the problems in economically recovering the nickel have previouslybeen thought to be insurmountable. The present invention offers thefirst economically feasible process for recovering nickel from asbestosore tailings. While the percentage of nickel present in the asbestos oretailings is small, the commercial utilization of the process will permitrecovery of large amounts of nickel per year, since vast quantities ofasbestos ore tailings are readily available every year.

DESCRIPTION OF THE DRAWING The drawing is a photmicicrograph of awaruiteparticles which have been separated from asbestos ore tailings inaccordance with the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Theprocess of this invention is useful for concentrating particles ofawaruite (FeNi found in asbestos ore, and in the tailings resulting fromasbestos ore-milling procedures. While the process can be used toconcentrate awaruite from extremely low percentages of awaruite in thestarting material, it

is desirable to select asbestos ore tailings that possess as high apercentage of nickel as is readily available. Generally, in selectingthe desirable asbestos ore tailings for use as starting materials,granular fractions are preferred because they pos sess somewhat highernickel contents than fibrous materials and sifter undersizes.

Preferably, the starting materials comprise tailings obtained afterasbestos ore has been fiberized and screened. Preferably, only theundersize material from the screening operation is utilized, butsometimes it may be advantageous to further crush and process oversizefractions also.

If the starting material for the process contains a significant amountof asbestos fiber, it is desirable to fiberize this material and removeit before proceeding to the magnetic separation step described below.Magnetic separation is hindered by the presence of fibrous materialwhich tends to bind the awaruite and serpentine particles together, orto trap small magnetic particles. A screening with aspirating step, insome instances combined with air separation, aids in putting the feed inthe optimum granular, fiber-free condition. Preferably, the feedparticle size is between 10 and mesh prior to the magnetic separationstep and the feed contains a minimum of fiber.

In accordance with the invention, the finely divided asbestos tailingsare magnetically separated to obtain a magnetically attracted,nickel-enriched fraction. This magnetic separation can be accomplishedby commercially available equipment such as discussed on pages 109]1093ofChemical Engineering Handbook, by John H. Perry, third Edition, Mc-Graw-Hill. Typical of such equipment is an enclosed belt-type magneticseparator manufacture by Eriez Manufacturing Co. and a high-intensityinduced roll magnetic separator manufactured by Carpco Manufacturing,Inc.

In one test, the awaruite content in the nickel-enriched frac' tion wasfound to be highest in +l00-mesh particles.

In accordance with the invention, the nickel-enriched fraction issubjected to mechanical impact to increase the maximum dimension of theawaruite particles and to fracture the remaining materials, mainlyserpentine rock, into smaller particles. It has been discovered that theawaruite is more malleable than the other major components of thenickel-enriched fraction, serpentine and magnetite, and that the softerawaruite particles do not accumulate an undesirable amount ofsmall-gauge particles during the procedure. When mechanically impacted,such as during ball-milling, the awaruite flattens and thereby enlargesin two dimensions. At the same time, the magnetite andserpentine tend toshatter intosmaller pieces, with the small pieces of magnetite andserpentine tending to form particles that are physically distinct fromthe awaruite particles.

Typically, a large portion of the awaruite particles is over 325-mesh insize after completion of the mechanical impacting step, while almost allof the physically distinct particles of magnetite and serpentine aresmaller than 325-mesh.

Preferably, the nickel-enriched fraction is mechanically im- 5 pacted byball or pebble-milling. The presence of fiber in the nickel-enrichedfraction tends to decrease the efficiency of the milling by becomingmore voluminous during processing and thus contributing a cushioningaction which damps the impact of the milling process on the serpentineor magnetite and is so undesirable that a dry-processing step to removefiber is advantageous if such an operation was not performed prior toeffecting the magnetic separation.

The exact milling procedure to be used for any given nickelenrichedfraction, depends on the particle sizes present in the charge, and theamount of fiber present in the nickel-enriched fraction. While ball orpebble-milling produces presently preferred results, other procedurescan be used to mechanically impact the nickel-enriched fractionincluding hammer 2O milling and centrifugal impact milling.

In accordance with the invention, the increased dimension awaruiteparticles are separated from the smaller particles of magnetite andserpentine by a size separation procedure, such as screening, orair-separation, or a combination of air-separa- 2 5 tion and screening.Preferably, because of the large quantities of material which usuallymust be size-separated, it is desirable to perform an air separationstep to reduce the quantity of material to be subjected to the finalsize-separation operation. The air-separation can be carried out on alarge scale at highfeed rates.

It has been found that air separators which rely on cyclones to make thecut are successful. For example, in one test procedure a heavy fractionwasrecovered which contained 60 percent by weight of the materialcharged to the air separator and 90 percent by weight of the nickel. Thelight or dust fraction was found to contain almost no recoverablenickel, that is nickel that would be recovered in an efficient finalwet-screening step.

The preferred final size separation step comprises wet screening on avery fine mesh screen, for example, a 65 to 400 mesh screen, with a325-mesh screen presently considered op timum. This wet-screening stepremoves most of the serpentine and magnetite and leaves the awaruiteparticles as the oversize fraction. Dry-screening and airjet-sievingprocedures 4 can be utilized in the final separation step, but possessproblems because the material tends to agglomerate.

For a clearer understanding of the invention, specific examples of itare set forth below. These examples are illustrative and are not to beunderstood as limiting the scope and underlying principles of theinvention in any way.

All percentages listed in the specification and claims are weightpercentages unless otherwise noted. All screen sizes are US. Standardunless otherwise noted.

EXAMPLE I The undersized material (0.23% Ni) from an ore screeningoperation using a screen of 28 mesh in a Quebec Chrysotile asbestos millis passed through a magnetic separator. A mag- 60 netic concentratecontaining 0.42 percent by weight of nickel is recovered. Analysis ofthe materials resulting from the magnetic separation operation is shownbelow in Table I:

The magnetic separation concentrated 30 percent of the nickel originallypresent into a nickel-enriched fraction com prising 17 percent by weightof the original sample. The

nickel-enriched fraction is then passed through a centrifugal impactmill manufactured by Entoleter, Inc. to subdivide or open the residualfiber bundles, making them more bulky and easier to subsequentlyseparate and remove.

After this operation the nickel-enriched portion is subjected to ascreening and aspirating operation to simulate standard asbestosrecovery techniques in which the bulky fiber tends to stratify above thegranular material on a shaking screen where it can be removed bysuction.

The screening and aspirating procedure produces a more concentratedfraction containing 0.70 percent by weight nickel. This 0.70 percentnickel fraction is ball milled in a small mill for 16 hours to produceflat, platelike particles of awaruite and to fracture the magnetite andserpentine rock remaining in the processed material. The ball-millingoperation is carried out dry.

After the ball-milling operation, the milled material is sent to amechanical air separator which separates the material into a heavyfraction that amounts to 15 percent by weight of the material charged tothe separator and contains 95 percent of the recoverable nickel.Subsequently, the air-separated material is subjected to a wet-screeningoperation using a 325- mesh screen. About 1 pound of material per ton ofcharged feed is recovered and this material contains about 50 percentnickel. The awaruite particles present in the product of this exampleare in the form of substantially flat shiny platelets, and have thegeneral shape illustrated in FIG. 1 of the drawings.

EXAMPLE ll Asbestos ore tailings comprising 28-mesh screen undersizedmaterials are magnetically concentrated to contain about 0.35% Ni and 50percent serpentine rock. Further concentration of the nickel isaccomplished by micropulverizing the material to liberate more awaruiteparticles and then screening the material on a nest of increasing meshscreens.

The magnetite and awaruite seem to concentrate in the finer fractionsproduced by micropulverizing. A nickel-enriched portion of 200-meshconcentrate is obtained by magnetically separating the pan fraction fromthe screening operation.

The serpentine content of the magnetically attracted frac tion isreduced to about 30 percent by the magnetic separation and the nickelpercentage is raised to about 3.5 percent.

This material containing 3.5 percent by weight of nickel is ball-milledwhile dry for about 72 hours and subsequently wetscreened through a325-mesh screen. Microscopic examination of the plus fraction showedthat the particles are platelike and silver-colored, and have thegeneral shape shown in FIG. 1. Spectographic analysis confirms that theparticles are almost completely awaruite. The actual nickel content ofthis plus fraction is percent, and the calculated composition is 79percent awaruite, 8 percent magnetite, and 8 percent serpentine. Thisprocedure produced a recovery of 0.4 percent of the original 28-meshtailings.

It is believed that the particles present in the plus fraction are allbasically awaruite particles. A small amount of fine gangue isapparently driven into the soft awaruite particles, however, to give aslightly impure product.

EXAMPLE III In this example, 66-mesh undersize asbestos ore tailingswhich would have had any large, heavy, awaruite particles alreadyscreened out, is used as the feed material. It is more fibrous and has alower magnetic content that the feed material of Examples I and II. Thismaterial is processed in accordance with the procedure of Example 1except that no air v separation step is utilized between theball-milling and the wet-screening. The ground concentrate is directlywetscreened to give an awaruite recovery amounting to 0.07 lbs. per tonof charged feed (about 0.04 lbs. nickel per ton of charged feed).

EXAMPLE IV Granular screen undersize feed as used in Example I isfiberized in a hammer mill and then passed through a mechanical airseparator to remove fiber and fines. The coarse fraction from theseparator is then magnetically separated to produce an enriched nickeland magnetite concentrate.

This concentrate is ball-milled dry in 100 pound quantities in a 2 footdiameter mill containing 1 inch and one-halfinch balls for three hours.The ground material is wet-screened to produce a 325-mesh oversizefraction that contains percent awaruite, 62% Fe O and 18 percentremainder, the major constituent of which remainder is serpentine. Thenickel produced is in the order of 15 percent of the fraction, or inother words, 75 percent of the awaruite.

EXAMPLE V The procedure of Example IV including the original screen ing,tiberization, air-separation, and magnetic separation is used to preparea feed material for the mechanical impact procedure.

In this example, the magnetic concentrate is wet-processed in IOO-poundquantities in the ball-mill described in Example IV for 1% hours, andthen wet-screened to obtain 325-mesh oversize fraction that contains anestimated 30 percent Ni.

lclaim:

l. A process for concentrating the nickel alloy awaruite found inasbestos ore tailings comprising:

a. magnetically separating the asbestos ore tailings to obtain amagnetically attracted, nickel-enriched fraction, and a waste fraction;

b. mechanically impacting the nickel-enriched fraction to increase themaximum dimension of the awaruite particles and to fracture theremaining materials into smaller particles; and

c. separating the increased-dimension awaruite particles from thesmaller particles of unwanted materials to recover an awaruite-richproduct.

2. The process of claim 1 in which the asbestos ore tailings consist ofparticles that pass a lO-mesh screen.

3. f l:he process of claim 1 in which the nickel-enriched frag- 6 tionis mechanically impacted by ball-milling to produce sub stantially flat,platelike particles of awaruite. g g

4. The process of claim 2 in which the nickel-enriched fraction ismechanically impacted by ball-milling to produce flat, platelikeparticles of awaruite.

5. The process of claim 3 in which the increased dimension awaruiteparticles are separated from unwanted materials by a procedure whichincludes wet screening.

6. A process for concentrating the nickel alloy awaruite found alongwith asbestos fiber, serpentine rock and magnetite in asbestos oretailings comprising:

a. magnetically separating the asbestos ore tailings to obtain amagnetically attracted nickel-enriched fraction, and a waste fraction;

b. fiberizing asbestos remaining in the nickel-enriched frac' tion;

c. removing asbestos fiber from the nickel-enriched fraction;

d. mechanically impacting the nickel-enriched fraction to increase themaximum dimension of the awaruite particles and to fracture theremaining materials into smaller particles; and

e. size separating the increased dimension awaruite particles from thesmall particles of unwanted materials to recover an awaruite-richproduct.

7. The process of claim 6 including a step in which asbestos in theasbestos ore tailings is fiberized and separated from the tailings priorto the tailings being magnetically separated to increase the efficiencyof the magnetic separation step.

8. The process of claim 6 in which the nickel-enriched fraction ismechanically impacted to produce substantially flat, platelike particlesof awaruite.

9. The process of claim 6 in which the size-separating step includeswet-screening the increased dimension awaruite particles from unwantedmaterials.

10. The process of claim 6 in which a dry nickeLenriched fraction ismechanically impacted by ball-milling.

2. The process of claim 1 in which the asbestos ore tailings consist ofparticles that pass a 10-mesh screen.
 3. The process of claim 1 in whichthe nickel-enriched fraction is mechanically impacted by ball-milling toproduce substantially flat, platelike particles of awaruite.
 4. Theprocess of claim 2 in which the nickel-enriched fraction is mechanicallyimpacted by ball-milling to produce flat, platelike particles ofawaruite.
 5. The process of claim 3 in which the increased dimensionawaruite particles are separated from unwanted materials by a procedurewhich includes wet screening.
 6. A process for concentrating the nickelalloy awaruite found along with asbestos fiber, serpentine rock andmagnetite in asbestos ore tailings comprising: a. magneticallyseparating the asbestos ore tailings to obtain a magnetically attractednickel-enriched fraction, and a waste fraction; b. fiberizing asbestosremaining in the nickel-enriched fraction; c. removing asbestos fiberfrom the nickel-enriched fraction; d. mechanically impacting thenickel-enriched fraction to Increase the maximum dimension of theawaruite particles and to fracture the remaining materials into smallerparticles; and e. size separating the increased dimension awaruiteparticles from the small particles of unwanted materials to recover anawaruite-rich product.
 7. The process of claim 6 including a step inwhich asbestos in the asbestos ore tailings is fiberized and separatedfrom the tailings prior to the tailings being magnetically separated toincrease the efficiency of the magnetic separation step.
 8. The processof claim 6 in which the nickel-enriched fraction is mechanicallyimpacted to produce substantially flat, platelike particles of awaruite.9. The process of claim 6 in which the size-separating step includeswet-screening the increased dimension awaruite particles from unwantedmaterials.
 10. The process of claim 6 in which a dry nickel-enrichedfraction is mechanically impacted by ball-milling.